* Nike shares surge after results, Amazon program
* Biotech declines hold back Nasdaq
* S&P tech sector set to post first monthly loss of year
* Indexes up: Dow 0.44 pct, S&P 0.35 pct, Nasdaq 0.21 pct (Updates to late afternoon)
June 30 (Reuters) - Major U.S. stock indexes were poised on Friday to end a volatile week on a high note, boosted by Nike's well-received quarterly report, with the S&P 500 set to post its best first half of the year since 2013.
Nike shares rose 11.3 percent after the world's largest footwear maker reported a quarterly profit that topped estimates and said it would launch a pilot online sales program with Amazon.com. Nike shares gave the biggest boost to the Dow industrials and the S&P 500.
A pullback in biotech shares, which had surged of late, limited the Nasdaq's gains.
The S&P technology index climbed 0.3 percent but was still on track to post its first monthly loss of the year. Tech has led the S&P 500's 8.4 percent rally this year, but its recent pullback suggests investors may be cashing in those profits to rotate to other sectors.
"Are we going to see a broadening of the rally, where you see more of the financials and other sectors fill in some of the gaps?" said Alan Lancz, president of Alan B. Lancz & Associates Inc., an investment advisory firm in Toledo, Ohio.
"It hasnt been a broad encompassing rally that I think investors will have to see a little bit more conviction rather than just in a handful of stocks," Lancz said.
The Dow Jones Industrial Average rose 93.2 points, or 0.44 percent, to 21,380.23, the S&P 500 gained 8.5 points, or 0.35 percent, to 2,428.2 and the Nasdaq Composite added 12.76 points, or 0.21 percent, to 6,157.11.
Industrials led gains among sectors, rising 0.9 percent, while financials lagged, falling 0.2 percent.
With the second quarter coming to a close, the S&P 500 was on track to record its biggest percentage first-half gain since climbing 12.6 percent in the first six months of 2013.
U.S. consumer spending rose modestly in May and inflation cooled, pointing to a slow-but-steady economic expansion. The Commerce Department data bolstered the view that the U.S. economy is rebounding in the second quarter.
Investors have been concerned about recent mixed economic data at a time that the Federal Reserve begins lifting interest rates from very low levels.
"In the next four to six weeks we'll get another set of economic data that will tell us if the Fed is justified in raising rates again this year," said Terry Sandven, chief equity strategist at U.S. Bank Wealth Management.
Second-quarter corporate results are set to begin in earnest in the coming weeks, with S&P 500 companies expected to post an 8-percent rise in earnings, according to Thomson Reuters I/B/E/S.
Advancing issues outnumbered declining ones on the NYSE by a 1.90-to-1 ratio; on Nasdaq, a 1.05-to-1 ratio favored advancers. (Additional reporting by Ankur Banerjee, Anya George Tharakan and Tanya Agrawal in Bengaluru; Editing by Arun Koyyur and Nick Zieminski)